Wednesday, March 21

Owls have surprisingly varied vocabularies, making the identification of heard-only birds prone to error. Two species sharing similar calls are the Eastern Screech-Owl and Northern Saw-whet Owl, both of which have whines/wails and short barks (kew/ksew) calls that could easily be confused.
The Eastern Screech-Owl wail is usually slightly tremulous at the end, which differentiates it from the very similar Northern Saw-whet Owl wail.(12.21am, Sep, PA)

Both species have "kew"-like calls or barks, also similar to each other.
Eastern Screech-Owl kew, with bill-snapping (5.15am, Aug, PA).

Adult at dusk calling in the vicinity of a calling fledgling (8.30pm, May, PA).

Northern Saw-whet Owl "ksew" calls (12.10am, Feb, PA)

The above recordings were of unseen birds, but are typical for each species. They emphasize the importance of obtaining recordings whenever possible to aid in confirming the identity of these and other nocturnal vocalizations.

Peterson Field Guide to Bird Sounds of Eastern North America. Nathan Pieplow, 2017. Highly recommended, includes almost all known vocalizations of eastern US birds, with spectrograms and detailed analysis. Excellent!

Stokes Field Guide to Bird Song, Eastern Region, by Lang Elliot. 3 CDs. Of commercial recordings, this has the most comprehensive collection of songs and calls.

The Birds of North America Online (BNA). Comprehensive information on all aspects of life history, including audio and video. By subscription.

The Singing Life of Birds. Donald Kroodsma, Houghton Mifflin, 2005. Terrific book (plus CD), a must read.

The Songs of Wildbirds. Lang Elliott., Houghton Mifflin, 2005. Excellent photos with high quality recordings including some rare ones such as the flight song of the Western Meadowlark.

The Sound Approach to Birding. A guide to understanding bird sound. A. van de Berg, M Constantine, M. Robb. Superb discussion of bird calls and song with 2 CDs.